The invention relates to a safety device for the drive unit of a vibration roller that has a switch lever for manually operation the drive unit, whereby the drive unit is forcibly switched off when a locking bar is in its switch-off position, from which it can be moved by an operator for operating and driving the roller against a permanent return force into a release position.
Safety devices of this kind are known from German Patent 34 42 083 C2.
In the known safety devices the blocking device in a first embodiment is comprised of a locking pawl that connects the coupling device with the control element and the switch lever in a form-fitting manner to a stationary housing as soon as it is moved into the locked engaged position with the locking bar by the operator. In a second embodiment the blocking device is comprised of a Hirth toothing one part of which is fixedly connected with the coupling device and the other part is fixedly connected to the housing whereby both parts, after displacement of the coupling device with the locking bar by the operator into the locked engaged position, come into contact.
When employing the first mentioned, constructively especially simple embodiment, the operator must pay close attention that, on the one hand, the normal engaged position of the coupling and not the disengaged position is adjusted when changes at the drive unit are performed. These difficulties are prevented with the aforementioned second embodiment having a blocking device with a Hirth toothing because the operator can move the switch lever in the engaged position of the coupling with a somewhat increased force expenditure when he slightly releases the force with which he supports the locking bar in its release position. The second embodiment however has the disadvantage that it requires an increased constructive expenditure and allows only a stepwise change at the drive unit.
It is an object of the invention to provide a safety device according to the preamble of claim 1 which is characterized by a simple construction as well as by the possibility of a continuous change of the drive unit.